1. Field of the Invention
The present invention relates to supply equipment for providing a stable supply of a solid organic metal compound in gaseous form which is a starting material for the formation of semiconductor film, superconductor film or the like of the compound.
The invention is also concerned with a method for providing a stable supply of a solid organic metal compound in gaseous form by using the supply equipment.
2. Description of the Prior Art
In recent years, the vapor deposition method in gaseous phase using an organic metal compound has remarkably progressed for film formation of semiconductor, super conductor or the like of the compound. Compound semiconductors are prepared by such methods as the so-called MOCVD (metal organic chemical vapor deposition) and MOMBE (metal organic molecular beam epitaxy methods). Using high-grade film controlling technique according to such methods, high-capacity semiconductor lasers, for example, are produced on a trial basis, some of which are now at a stage of large-scale production. Extensive studies have also been done on the formation of semi-conductors that have physical properties never existing in nature by artificially controlling the film on the level of atom layer. It is expected that such semiconductors will soon be in practical use.
Vessels for supplying to the film-formation apparatus vapor of an organic metal compound which is a starting material for the film of semiconductor, for example, by transporting it by the use of the vapor pressure by means of carrier gas (shown in FIG. 4) usually involve introducing through a capillary carrier gas that is inert to said organic metal compound into the liquid organic metal compound and collecting it after removed from the vessel in association with said carrier gas.
Heretofore, organic metal compounds that are solid at ordinary temperature such as, for example, trimethylindium (m.p. 88.4.degree. C.) in general have been treated by the use of sublimation pressure in a vessel similar to the one for organic metal compounds that are solid at ordinary temperature.
In the vapor deposition method for forming film, for example, of compound semiconductor or superconductor using an organic metal compound in gaseous phase it is desired to provide stable and continuous supply in gaseous phase to the film-formation apparatus of vaporized organic metal compound feed which compound is solid or liquid in nature.
There has been in the prior-art method using a vessel as shown in FIG. 4 when a solid organic metal compound is used as the starting material a problem that the carrier gas is apt to be ventilated through crystals of the starting material thereby causing channelling with a result that outlet vapor is not a saturated one. Poor controllability due to variation in flow rate of the carrier gas and low stability in the degree of saturation have also been problematic.
Such unstability behaviors occurred more frequently as the organic metal compound was used more with less amount remained in the vessel. Therefore, they produced bad influence upon controllability and reproducability in the film-formation reaction using a gaseous organic metal compound.
The object of the invention is to provide equipment for supplying, for example, to film-formation equipment, feed gas substantially saturated with an organic metal compound in a constant concentration of the saturated gas at a stable flow rate even when flow rate of the carrier gas or remaining amount of the organic compound in the vessel are changed and a method for providing such supply.